Metabolic changes in pathological states can be very complex, as is increasingly revealed by modern techniques such as liquid-chromatography mass spectrometry. It is becoming clear that fingerprinting by metabolomics will play a greater role in tracking and diagnosing an individual’s health status as it provides a direct functional read-out of the physiological status of an organism. The identification of specific metabolomics ‘signatures’ in response to challenges such as a high fat diet (HFD), exercise, drug abuse, or diseases is important for the discovery of biomarkers. In this context, it is crucial to note that the metabolic status varies during the day, which makes it necessary to record time-resolved metabolomes.
Another point is that usually, only blood serum can be sampled, and the metabolic status of organs and tissues such as skeletal muscle must be deduced from small molecules found in the serum. Sato, Parr, et al. analyzed the metabolome levels of human serum and skeletal muscle in the morning and evening in response to divergent nutritional challenges in order to identify unique signatures present in serum and muscle. Their findings illustrate how the changes in metabolomics in response to nutritional challenges are dependent on the time of the day. They report a remarkable consistency among the individuals participating in the study when taking into account their day-night metabolic profiles and responses to nutritional challenges.